Antioxidant and extreme pressure lubricating oil additive

ABSTRACT

1. A COMPOSITION COMPRISING A MAJOR AMOUNT OF AN OIL OF LUBRICATING VISCOSITY AND FROM 0.02 TO 5 PERCENT BY WEIGHT OF THE PRODUCT OF THE PROCESS WHICH COMPRISES CONTACTING AN ALKYLPHENOL, MERCAPTOBENZOTHIAZOLE AND AN ALDEHYDE IN THE MOLE RATIO OF ABOUT 1-2:1:1-2 AT A TEMPERATURE OF FROM ABOUT 250* TO ABOUT 300*F. FOR A PERIOD OF 2-20 HOURS FOLLOWED BY THE ADDITION OF SULFUR MONOCHLORIDE IN THE AMOUNT OF 0.25-2 MOLES PER MOLE OF MERCAPTOBENZOTHIAZOLE AT 100-200*F.

United States Patent 3,846,318 ANI'IOXIDANT AND EXTREME PRESSURE LUBRICATING OIL ADDITIVE Warren Lowe, El Cerrito, Calif., assignor to Chevron Research Company, San Francisco, Calif. No Drawing. Filed Apr. 11, 1973, Ser. No. 350,223 Int. Cl. Cm 1/38 US. Cl. 252-475 3 Claims ABSTRACT OF THE DISCLOSURE An ashless, phosphorus-free material having antioxidant and extreme pressure properties as a lubricating oil additive is produced by the reaction of mercaptobenzothiazole, an aldehyde and a phenol.

BACKGROUND OF THE INVENTION Field of the Invention Description of the Prior Art Certain benzothiazole sulfides are known EP lubricat: ing oil additives,'U.S. Pat. 2,704,745.

SUMMARY OF THE INVENTION A phosphorus-free ashless derivative of mercaptobenzothiazole is provided which finds use as an extreme pressure agent and an antioxidant additive in lubricating oils. The' additive is the reaction product of mercaptobenzothiazole, an aldehyde, and a phenol. The mercaptobenzothiazole maybe alkylated, as may the phenol, with a C C alkyl group. The reaction product is an outstanding oxidation inhibitor which provides satisfactory extreme pressure properties, and unlikethe parent compound is sufiicient soluble in lubricating oils. Extreme pressure and antiwear properties of the additive are somewhat improved by the incorporation of more sulfur, as by the reaction of the product with sulfur monochloride.

" DESCRIPTION OF THE PREFERRED EMBODIMENTS v The compounds of this invention are derived from a mercaptobenzothiazole of the general formula:

alkylphenol. Because of the existence of 'tautomerism in rriercaptob'enzothiazole, and the probability of reaction at "ice both the ortho and para positions of the phenol, the con densation product has a complex composition not representable by a structural formula. As used herein, the term condensation product means the product obtained by reacting together an alkylphenol, a mercaptobenzothiazole, and an aldehyde. The order of the reaction is of' no consequence herein, since the reactants are blended together in the formation of the condensation product The phenol used as reactant may have none, one, or

more substituent alkyl groups: the alkyl substituents are" aliphatic groups having in total from 1 to 36 carbon atoms.

Each of the alkyl groups of the alkylphenols may con-' tain from 1 to 24 carbon atoms. The phenol may be ortho substituted, para substituted, or ortho-para substituted, and' is preferably an alkylphenol or dialkyl phenol.

Examples of alkyl groups of the alkylphenols includei methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, tertiary butyl, octyl, dodecyl, tetradecyl, hexadecyl, octadecyl, butenyl, octenyl, dodecenyl, tetradecenyl, octadecenyl, butenyl oligomers containing from 12 to- 16 carbon atoms, etc.

Examples of alkylphenols include paracresol, methylphenol, dimethylphenol, trimethylphenol, isopropylphenol, ethylphenol, diethylphenol, diamylphenol, triamylphenol, octylphenol, methyloctaphenol, dodecylphenol, octadecylphenol, vinylphenol, butenylphenol, octadecenylphenol, polybutylenephenol, wherein the polybute nyl groups contain from 12 to 16 carbon atoms, etc.

The aldehyde reactant is preferably formaldehyde and it may be used as such in thereaction, that is, as gaseous formaldehyde, or as the active solution of formaldehyde. Also, compounds which yield formaldehyde such as paraformaldehyde may be used. As is known to those skilled in the chemical arts, the Mannich condensation is a general reaction of aldehydes and certain ketones, as well as amines and compounds having reactive hydrogen atoms.

Typical aldehydes which find use in the practice of the" in the benzene ring. These alkyl radicals may be saturate'd or unsaturated aliphatic groups having a'total of from" 1 to 36 carbon atoms. Each of the alkyl radicals-may 'con-' tain from 1 to 24 carbon atoms. It is preferred that the from'12 to 18 carbon atoms. Examples of such alkyl nols, mercaptobenzothiazoles and aldehydes are' prese'n t in the reaction mixture in a mole ratio of from approxi-- mately 1':l:1 to about 2:1:2. The phenolmerc'aptobenz'o'--" aldehyde condensation product is prepared by forming an admixture of the reactants and heating said mixture for a period of from about 2 to about 20 hours at temperatures ranging from 200 to 300 and preferably from about 250 to about 300 F. In a preferred method of synthesis, the reaction mixture also contains a small".

amount (less than 3 weight percent based on the weight of the reaction mixture) of an amine which is found to.- act as acatalyst for the reaction. Such catalytic amines include C C alkyl amines and polyalkylene polyamines, such as butyl amine and hexamethylene tetramine. V The extreme pressure and antiwear properties of the additive are improved by the incorporation of more sulfur into the product, as by the reaction of the product with a sulfurizing agent such .as sulfur monochloride (S Cl PSCl' 8, P 8 etc. In general, from 0.25-2 moles of sulfur monochloride are reacted per mole of mercaptobenzd thiazole in the product at a' temperature of about 3 200 F. neat or in a suitable solvent such as benzene or xylene.

The lubricating composition is obtained from this reaction product by mixing the product directly with the oil at room temperature or higher until a continuous phase is formed.

Lubricating oils which are suitable base oils for the compositions of this invention include a wide variety of lubricating oils, such as naphthenic base, paraflin base, and mixed base; other hydrocarbon lubricants, e.g., lubricating oils derived from coal products; and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc. and mixtures thereof), alkylene oxide-type polymers, dicarboxylic acid esters, liquid esters of acids of phosphorus, alkylbenzene polymers, polymers of silicon, silicones, etc. Synthetic oils of the alkylene oxidetype polymers which may be used include those exemplified by the alkylene oxide polymers (e.g., propylene oxide polymers) and derivatives, including the alkylene oxide polymers prepared by polymerizing the alkylene oxides in the presence of water or alcohols. The above base oil types may be used individually as such or in various combinations wherever miscible or wherever made so by the use of mutual solvents. The general requirement for oils used in compositions of this invention is that they be fluids of lubricating viscosity, generally having viscosities from about 35 to 50,000 Saybolt Universal Seconds (SUS) at 100 F.

Usually included in the oils besides the subject additives are such additives as rust inhibitors, additional antioxidants, oiliness agents, detergents, foam inhibitors, viscosity index improvers, pour point depressants, etc. Usually these additives will be present in the range from about 0.1 to 20 weight percent, more usually from about 0.5 to 15 weight percent of the total composition. Generally, each of the additives will be present in the range of from about 0.01 to weight percent of the total composition.

The compounds of this invention will generally be present in lubricating oils in the range of about 0.5 to 5 weight percent of the total composition. However, the compositions may be prepared as oil concentrates for dilution before use as lubricants in which case these additives may be present in amounts much higher than 5 percent.

The examples presented hereinbelow illustrate the preparation of the phenol-mercaptobenzothiazole-aldehyde condensation product and the formation of lubricating composition by the use of such condensation products.

EXAMPLE 1 EXAMPLE 2 A mixture consisting of mercaptobenzothiazole, tetrapropenyl phenol, paraformaldehyde and hexamethylene tetramine in the amounts given in Example 1 is stirred for four hours at 280 plus or minus 5 F. under nitrogenI A total of 36 ml. of water is collected in the first two hours. The product is stripped to 250 F. under vacuum. The product weighs 949 grams and analyzes as 12.5 percent sulfur and 2.71 percent nitrogen.

EXAMPLE 3 To a mixture of 478 grams of product prepared substantially as in Examples 1 and 2 in 600 ml. of benzene, 206 grams of tri-ethylamine is added and 67.5 grams of S Cl is added in 100 ml. of benzene from a dropping funnel. The temperature of the mixture is kept below 140 -F. during the addition of S 01 over 15 minutes. The mixture is then stirred for 1 hour and minutes at room temperature and refluxed (185-189 F.) for 12 hours. The product is diluted with two liters of benzene, allowed to settle, filtered and stripped to 250 F. under vacuum. 519 grams of product is obtained, 0.09% chlorine by weight.

EVALUATION In order to demonstrate the effectiveness of the compounds of this invention in inhibiting oxidation, samples of the condensation product of Example 1 were formed into a lubricating oil composition and subjected to an oxidation test. The Oxidator B Test is our laboratory designation for a test measuring resistance to oxidation by means by a Dornte-type oxygen absorption apparatus (R. W. Dornte, Oxidation of White Oils, Industrial and Engineering Chemistry, Vol. 28, p. 26, 1936). The test conditions are one atmosphere of pure oxygen at 340 F. and one reports the hours to absorption of one liter of 0 by 100 grams of oil as the Oxidator B Lifetime in hours. In the Oxidator B Test a catalyst is used and a reference additive package is included in the oil. The catalyst is a mixture of soluble metal-naphthenates simullating the average metal analysis of used crankcase oils. Thus, the method measures the response to conventional inhibitors in a simulated application. The results are given in Table I where the composition of the present invention is compared to composition containing no antioxidant and a commercial antioxidant of the hindered phenol type. The great superiority of the antioxidant of the present invention is evident.

1 Base oil composition of neutral mineral oils having aniline point of about 220 F., 43% by wt. having a viscosity of? about 100 SUS at 100 F.

V and 57% having a viscosity of 200 SUS at 100 I Time in hours for uptake of 1 liter of oxygenllOO g. of oil at 340 F. a Three hours of immersion of copper strip in composition at 250 F.

An important requirement of lubricating oil and grease additives is that they do not corrode silver or coppercontaining bearings. In the silver corrosion test, strips of silver are immersed in two lubricating compositions, one containing the additive of the present invention and the other not containing that additive for the same period of time at 340 F. The strips are weighed before immersion, after immersion, and after washing with KCN. The measured Weight loss in milligrams determines the degree to which the lubricating composition corrodes. A similar test is carried out with copper strips immersed for three hours in the composition at 250 However, in the case of the copper corrosion test, the copper corrosion rating is based on the discoloration of the copper in comparison to the ASTM D130 Copper Strip Corrosion Standards. These corrosion tests are reported in Tables I and II.

TABLE II.SILVER CORROSION TEST Weight loss, mg.

Beiore KCN After KON Base oil 141. 3 173. 9 Example 1, 1% by wt. in base oil 9.7 16. 8

l 480 SUS at F. neutral petroleum oil with 20 mm./kg. of zinc bis- (polypropenylphenyl) dithiophosphate.

The additive was also tested as an automatic transmission fluid additive. The typical automatic transmissionv per Corrosion Test and the well-known Four-Ball Wear Test and Timken Wear Test are summarized in Table III.

TABLE III.-TESTS OF AUTOMATIC TRANSMISSION FLUID 800 r.p.m.) (Pass is 1.25 mm. or less).

The test results amply demonstrate the ability of the additive of the present invention to function as an extreme pressure and antiwear agent for lubricating oils, greases and functional fluids.

The condensation product of the present invention was also tested as a possible antioxidant additive in lubricating oils for the internal combustion engine. Table IV compares the oxidation inhibitor of the present invention to the di-tert-butyl bis-phenol antioxidant of Table I and to the base oil containing no oxidation inhibitor. The base oil formulation consisted of a 480 SUS at 100 F. neutral petroleum oil containing 8 percent of a polyisobutenyl succinimide of triethylene tetramine ashless dispersant and 20 rum/kg. of tricresyl phosphate. The engine test is the 280-BMEP Caterpillar Engine Test. This is a severe Caterpillar diesel engine test, run for 16 hours at 1200 rpm, 280 brake mean effective pressure in p.s.i., water temperature of the cooling jacket, 190 F., sulfur content of the fuel, 0.4 percent and fuel input at a rate which provides 6,900 B.t.u./minute. In Table IV, the rating of groove deposits is based on a scale of -100, 100 being completely filled grooves. The rating for land deposits is based on a range of O-800, 800 being completely black. The rating for underhead deposits is based on a range of 0-10, 10 being completely clean. The top land, here shown with high ratings. is subject to bounce so that the second and third lands are more reliable indicators of engine cleanliness.

TABLE IV.CATERPILLAR ENGINE TEST Under- Land head Inhibitor Groove deposits deposits rating 1% di-tert-butyl bis-phenol- 11. 6, 6. 5, 0 6, 0 2605(] 7. 1 1% Example 1 8. 2, 1. 5, 0. 5, 0 5 2355--10 9. 5 None l7. 6, l. 3, 0. 5, O 5 85-10-10 3. 3

TABLE V Falex Oxidator Four-ball B hours 4 Wear 5 Shear 6 wear Base oil 1 0. 4-0. 7 18 900 0. 47 Additive (at 1 wt. in base 1 13185;) SUIS at 100 nefutral petroleum oil, 5 weight percent of polyso u eny suceinimi e0 tetraeth l 0.1 t f terephthalic acid y ene pentamme, and percen o 2 Product roduced subst t with S2012 p an rally as in Examples 1 and 2 before reac 3 Product of footnote 2, after reaction with S2012,

4 Time in hours to uptake of 1 liter 0 e 6 Falex pin weight loss in mg. xyg 11,100 g of 011 at 340 F. 0 Falex load to failure in pounds.

v rage diameter of scar in mm., 1800 r.p.m., 20 kilograms load at 130 F- r 1 hour.

While the given examples illustrate specific syntheses of the preferred embodiments of this invention, they are intended to be illustrative rather than exhaustive. The test results amply illustrate the superiority of the condensation products of the present invention as lubricating oil and grease additives, and as functional fluid additives. In addition to those illustrated, other reaction products formed from the specified reagents of the present invention would also perform as superior extreme pressure agents, anti-wear additives and oxidation inhibitors. It is not possible to attempt a comprehensive catalogue of such reactants or to describe the invention in terms of specific chemical names of such reactants and reaction products without producing a voluminous disclosure. One skilled in the art could, by following the teaching of the invention herein described, select the proper reactants and reaction conditions to provide a useful composition for his purpose. While the character of this invention has been described in detail with several examples, this has been done by way of illustration rather than limitation. It would be apparent to those skilled in the art that numerous modifications and variations of the illustrative examples can be made in the practice of the invention within the scope of the following claims.

What is claimed is:

1. A composition comprising a major amount of an oil of lubricating viscosity and from 0.02 to 5 percent by weight of the product of the process which comprises contacting an alkylphenol, mercaptobenzothiazole and an aldehyde in the mole ratio of about 1-2: 1:1-2 at a temperature of from about 250 to about 300 F. for a period of 2-20 hours followed by the addition of sulfur monochloride in the amount of 025-2 moles per mole of mercaptobenzothiazole at 200 F.

2. A composition comprising a major amount of an oil of lubricating viscosity and from 0.02 to 5 percent by weight of the product of the process which comprises contacting an alkylphenol, or dialkylphenol, wherein said alkyl group contains from 1 to 24 carbon atoms, mercaptobenzothiazole and an aldehyde selected from the group consisting of formaldehyde, paraformaldehyde, benzaldehyde, acetaldehyde and 2-ethylhexanal, in the mol ratio of about 1-2:1:1-2 at a temperature of from about 250 to about 300 F. for a period of 2-20 hours followed by the addition of sulfur monochloride in the amount of 025-2 mols per mol of mercaptobenzothiazole at 100200 F.

3. A composition comprising a major amount of an oil of lubricating viscosity and from 0.02 to 5 percent by weight of the product of the process which comprises contacting tetrapropenylphenol, mercaptobenzothiazole and paraformaldehyde in the mol ratio of about 1-2:1:1-2 at a temperature of from about 250 to about 300 F. for a period of 2-20 hours, followed by the addition of sulfur monochloride in the amount of ().25-2 mols per mol of mercaptobenzothiazole at 100200 F.

References Cited UNITED STATES PATENTS 8/1952 Woodrutf et a1. 25247.5 1/1949 Oberright.

OTHER REFERENCES W. H. CANNON, Primary Examiner US. Cl. X.R. 

1. A COMPOSITION COMPRISING A MAJOR AMOUNT OF AN OIL OF LUBRICATING VISCOSITY AND FROM 0.02 TO 5 PERCENT BY WEIGHT OF THE PRODUCT OF THE PROCESS WHICH COMPRISES CONTACTING AN ALKYLPHENOL, MERCAPTOBENZOTHIAZOLE AND AN ALDEHYDE IN THE MOLE RATIO OF ABOUT 1-2:1:1-2 AT A TEMPERATURE OF FROM ABOUT 250* TO ABOUT 300*F. FOR A PERIOD OF 2-20 HOURS FOLLOWED BY THE ADDITION OF SULFUR MONOCHLORIDE IN THE AMOUNT OF 0.25-2 MOLES PER MOLE OF MERCAPTOBENZOTHIAZOLE AT 100-200*F. 